whatever you measure under the bust is your back size - may have to round up/down if you are an odd number depending on the fit of the bra. e.g. measure 30" = 30 back size

Cup size goes up in 1" increments e.g. 1 inch difference between the back size and over bust gives an A cup, 2 inch difference gives a B cup, etc

In the UK the cup sizes tend to go AA (where back and cup size are less than an inch different), A, B, C, D, DD, E, F, FF, G. GG, H, HH, J, K, KK, L although not all manufacturers offer all the different cup sizes and jump straight from F to G, etc

In the example above 30 is the back size and the cup size is between 8 and 9 inches different which could be a FF or G cup depending on the bra itself.

I really don't see how this can work! I've been reading the bra threads and measured my self 30 under bust - but I can barely even do up the one 34 bra I have? According to this way of measuring I should be 30D, but as I said,I can hardly do up (never mind breathing) the 34D I have, and my feeble boobs in no way fill the cup, no matter what scooping I do.

Okay just measured mine. 36" around ribcage and 43" leaning forward makes me a 36 f? I would never fill a 36f. I usually wear a 38C and it's comfortable with no overspill or back fat. I don't get digging in around the ribcage or cup over spill.

Sorrel, thank you so much. I honestly couldn't believe I would fit in such a size, but I found a 30f to be great in a t shirt style. The shop assistants were all commenting to each other when I asked for the sizes and were looking at me as if saying 'she's never an f'. I dont think they liked me not asking for their help tbh, but they were doing the adding band inches to the lady in the next cubicle, so no way!

Just waiting in the checkout queue I cant belive how many women were wearing and buying such obviously wrong sized bras. I am a true convert.

Thank you! I cant believe how much my clothes fit better too. DH thought i'd bought a new top saying how nice it looked....I went shopping in it but put my new bra on before I got home!

I'm currently dieting, I have about 4 stone to lose. So how often should I get new bras? The one I have at the moment is horribly uncomfortable, it feels like it rubs and I can pull the gore (?) about an inch away from my body. But I can't for the life of me do my bras up at the back and if I try a smaller back size and do it up at the front I can't then turn it round

MrsH i'm in the losing weight boat myself. It kind of depends how you lose weight tbh - mine always goes from my back size first. On that basis if I was between sizes I would go for the smaller band (maybe with an extender) and then tighten through the hooks as I lost weight.

However, thanks to places like brastop you can get good bras at relatively cheap prices and you will generally feel better about yourself if they fit right so it might be worth roughly keeping your size correct but only buying a couple at a time

Can someone explain "scooping" and how much you should be able to stretch the band away from body. I've come out as 36E/38D I think. I am wearing 38B which feels smooth in cup but there is a gap of flesh between edge of cup and underarm and wires don't sit flat against body underneath and ride up.

Ok, several signs your bra is wrong there. The flesh between underarm and cup needs to be in the cup. The wires riding up mean the band is too big. In terms of scooping - scoop everything you can! If it will go forward then forward it goes.

Try it in your current bra - you should find you have substantial quad boob after scooping I would expect

When the bra is on back to front (easiest way to appraise it) you should only be able to stretch the band a couple of inches.